Cement compositions comprising improved lost circulation materials and methods of use in subterranean formations

ABSTRACT

Cement compositions that include improved lost circulation materials are provided. In certain exemplary embodiments, the improved lost circulation materials include inelastic particles of polyethylene, polystyrene, and/or polypropylene. Optionally, the cement compositions also may include additives such as fly ash, a surfactant, a dispersant, a fluid loss control additive, a conventional lost circulation material, an accelerator, a retarder, a salt, a mica, fiber, a formation-conditioning agent, fumed silica, bentonite, expanding additives, microspheres, weighting materials, or a defoamer.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional patent application of commonly-ownedU.S. patent application Ser. No. 10/802,903, filed Mar. 17, 2004 nowU.S. Pat No. 6,902,002, entitled “Cement Compositions ComprisingImproved Lost Circulation Materials and Methods of Use in SubterraneanFormations,” by Jiten Chatterji, et al., which is incorporated byreference herein for all purposes.

BACKGROUND OF THE INVENTION

The present invention relates to subterranean cementing operations and,more particularly, to cement compositions comprising improved lostcirculation materials, and methods of using such cement compositions insubterranean formations.

Hydraulic cement compositions commonly are utilized in subterraneanoperations, particularly subterranean well completion and remedialoperations. For example, hydraulic cement compositions are used inprimary cementing operations whereby pipe strings such as casings andliners are cemented in well bores. In performing primary cementing,hydraulic cement compositions are pumped into the annular space betweenthe walls of a well bore and the exterior surface of the pipe stringdisposed therein. The cement composition is permitted to set in theannular space, thereby forming an annular sheath of hardenedsubstantially impermeable cement therein that substantially supports andpositions the pipe string in the well bore and bonds the exteriorsurface of the pipe string to the walls of the well bore. Hydrauliccement compositions also are used in remedial cementing operations suchas plugging highly permeable zones or fractures in well bores, pluggingcracks and holes in pipe strings, and the like.

Subterranean formations traversed by well bores often may be weak,highly permeable, and extensively fractured. In some cases, suchformations may be unable to withstand the hydrostatic pressure normallyassociated with fluids (e.g., cement compositions and the like) beinginjected into the formation. In such cases, the hydrostatic pressure maybe sufficient to force such fluids into the natural or created fracturesand/or permeable zones of the formation, which may result in asignificant loss of fluid into the formation. This loss of fluidcirculation may be problematic for a number of reasons. For example,where the loss of circulation occurs during a cementing operation,excessive fluid loss may cause a cement composition to dehydrateprematurely. Premature dehydration of the cement composition mayexcessively viscosify the cement composition, and potentially may causean operator to terminate the cementing operation, wash out the cementcomposition from the well bore, and restart the cementing operationanew.

Previous attempts to minimize the loss of circulation into thesubterranean formation have involved adding a variety of additives,including, but not limited to, asphaltenes, ground coal, cellulosicmaterials, plastic materials, walnut hulls, sized waste formica, and thelike, to the cement composition. Such additives have been included, forexample, to attempt to plug or bridge formation fractures and/or thepermeable zones in the formation where the treatment fluids typicallymay be lost. However, conventional materials often are not rigid, andthus a greater concentration of these materials may be required toeffectively prevent the loss of circulation during a cementingoperation.

Polyethylene is used extensively in manufacturing, for instance, trashcans, buckets, baskets, and other materials of commerce. With time, theplasticizer that often is a component of a typical polyethylene productmay begin to degrade, which may cause the polyethylene to becomeincreasingly brittle, which may reduce its usable life. Consumersgenerally have no use for brittle polyethylene materials and oftendiscard or otherwise dispose of them, commonly in a landfill, where thepolyethylene may reside indefinitely, because it generally does notdeteriorate until after a very long time.

SUMMARY OF THE INVENTION

The present invention relates to subterranean cementing operations and,more particularly, to cement compositions comprising improved lostcirculation materials, and methods of using such cement compositions insubterranean formations.

An example of a composition of the present invention comprises a cementcomposition comprising a hydraulic cement, an inelastic lost circulationmaterial, and water.

Another example of a composition of the present invention is a lostcirculation material comprising inelastic polyethylene, polystyrene,and/or polypropylene particles.

The features and advantages of the present invention will be readilyapparent to those skilled in the art upon a reading of the descriptionof the preferred embodiments that follows.

DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention relates to subterranean cementing operations and,more particularly, to cement compositions comprising improved lostcirculation materials, and methods of using such cement compositions insubterranean formations.

The cement compositions of the present invention generally comprisewater, a hydraulic cement, and an improved lost circulation material ofthe present invention. Optionally, other additives may be included, suchas fly ash, silica, fluid loss control additives, surfactants,dispersants, accelerators, retarders, salts, and the like.

The water utilized in the cement compositions of the present inventioncan be fresh water, saltwater (e.g., water containing one or more saltsdissolved therein), brine (e.g., saturated saltwater), or seawater.Generally, the water can be from any source provided that it does notcontain an excess of compounds (e.g., dissolved organics, such astannins) that may adversely affect other components in the cementcomposition. Further, the water may be present in an amount sufficientto form a pumpable slurry. In certain exemplary embodiments, the wateris present in the cement compositions of the present invention in anamount in the range of from about 30% to about 180% by weight of thecement (“bwoc”) therein. In certain exemplary embodiments, the water ispresent in the cement compositions of the present invention in an amountin the range of from about 40% to about 90% bwoc therein. In certainexemplary embodiments, the water is present in the cement compositionsof the present invention in an amount in the range of from about 40% toabout 60% bwoc therein. One of ordinary skill in the art, with thebenefit of this disclosure, will recognize the appropriate amount ofwater for a chosen application.

Any cements suitable for use in subterranean applications are suitablefor use in the present invention. In certain exemplary embodiments, theimproved cement compositions of the present invention comprise ahydraulic cement. Suitable examples of hydraulic cements that may beused include, but are not limited to, those that comprise calcium,aluminum, silicon, oxygen, and/or sulfur, which set and harden byreaction with water. Examples include, but are not limited to, Portlandcements, pozzolanic cements, gypsum cements, calcium phosphate cements,high alumina content cements, silica cements, high alkalinity cements,and mixtures thereof.

The cement compositions of the present invention further comprise animproved lost circulation material of the present invention. Generally,the improved lost circulation materials of the present inventioncomprise any inelastic material that provides a desired level of controlof the loss of circulation from the cement composition into theformation, with minimal adverse impact to the properties of the setcement. Among other things, certain embodiments of the lost circulationmaterials of the present invention may bridge and/or plug fractures andpermeable zones in the formation zone so as to minimize the loss offluid circulation into the formation. In certain exemplary embodiments,the lost circulation materials of the present invention have a densitysuch that they do not rise to the surface of the well bore ifcirculation of the cement composition should cease. Generally, the lostcirculation materials of the present invention may have a particle sizedistribution that provides a desired level of lost circulation control.In certain exemplary embodiments, the lost circulation materials of thepresent invention may have a particle size distribution in the range offrom about 100 microns to about 5,000 microns. In certain exemplaryembodiments, the lost circulation materials of the present invention mayhave a particle size distribution in the range of from about 200 micronsto about 2,500 microns.

In certain exemplary embodiments, the lost circulation materials maycomprise inelastic polyethylene, polypropylene, and/or polystyreneparticles. In certain exemplary embodiments wherein the lost circulationmaterials comprise inelastic polyethylene particles, a variety of typesof inelastic polyethylene particles may be suitable for use inaccordance with the teachings of the present invention, including, butnot limited to, waste polyethylene (e.g., polyethylene materials thathave been discarded, for example, for deposit in a landfill). Suitableinelastic polyethylene particles are commercially available from, interalia, Forta Corporation in Grove City, Pa. Polyethylene particles mayhave a melting point of about 280° F. Accordingly, in certain exemplaryembodiments wherein the lost circulation materials of the presentinvention comprise waste polyethylene particles, such embodiments may beparticularly suitable for use in cementing operations wherein the bottomhole circulation temperature is below about 260° F.

In certain exemplary embodiments, the lost circulation materials of thepresent invention may comprise waste polyethylene particles that havebeen granulated and sized using any suitable means (e.g., a granulator,a rotary mill, and a vibrating shaker screen). In certain instances, anoperator may elect to reduce the size of polyethylene materials to adesirable size by using, e.g., a rough mill or knife hog before feedingthem into the granulator. Within the granulator, multiple knives may cutand grind the polyethylene into smaller pieces. Generally, thepolyethylene may remain inside the granulator, while its size iscontinually reduced, until the granulated particles have been reduced insize so as to pass through an exit screen that limits the maximum outputsize of the granulator to a desired size. In certain exemplaryembodiments, the polyethylene particles further may be sized and sortedusing, e.g., vibrating shaker screens. Exemplary methods of granulationand sizing may be found in U.S. Pat. No. 3,042,608, the relevantdisclosure of which is hereby incorporated by reference.

In certain exemplary embodiments, the lost circulation materials of thepresent invention may comprise fine, medium, or coarse particles, or amixture thereof. As referred to herein, the term “fine-sized particles”will be understood to mean particles having an average size in the rangeof less than about 150 microns. As referred to herein, the term“medium-sized particles” will be understood to mean particles having anaverage size in the range from about 250 microns to about 850 microns.As referred to herein, the term “coarse-sized particles” will beunderstood to mean particles having an average size in the range ofgreater than about 1,100 microns. In certain exemplary embodiments, thelost circulation materials of the present invention may comprise about45% to about 55% medium-sized particles by weight of the lostcirculation material and about 45% to about 55% fine-sized particles byweight of the lost circulation material. In certain exemplaryembodiments, the lost circulation materials of the present invention maycomprise about 45% to about 55% coarse-sized particles by weight of thelost circulation material and about 45% to about 55% fine-sizedparticles by weight of the lost circulation material. In certainexemplary embodiments, the lost circulation materials of the presentinvention may comprise about 45% to about 55% coarse-sized particles byweight of the lost circulation material and about 45% to about 55%medium-sized particles by weight of the lost circulation material. Thechoice of a particular mixture of particle sizes may depend on a varietyof factors, including, inter alia, the cement composition and formationtype. One of ordinary skill in the art, with the benefit of thisdisclosure, will be able to identify a suitable mixture of particlessizes for a particular application.

The lost circulation materials of the present invention may be added tothe cement compositions of the present invention in a variety of ways.In certain exemplary embodiments, the lost circulation materials may bedry-blended with the cement composition prior to the addition of thewater. Generally, the lost circulation materials of the presentinvention may be present in the cement compositions of the presentinvention in an amount sufficient to provide a desired level of lostcirculation control. In certain exemplary embodiments, the lostcirculation materials of the present invention may be present in thecement compositions of the present invention in an amount in the rangeof from about 1 pound to about 10 pounds per sack of cement. In certainexemplary embodiments, the lost circulation materials of the presentinvention may be present in the cement compositions of the presentinvention in an amount in the range of from about 4 pounds to about 6pounds per sack of cement. One of ordinary skill in the art, with thebenefit of this disclosure, will recognize the appropriate amount of thelost circulation materials of the present invention to use for a chosenapplication.

Optionally, the cement compositions of the present invention further maycomprise a conventional lost circulation material. The conventional lostcirculation material may be any material that may minimize the loss offluid circulation into the fractures and/or permeable zones of theformation. Examples of suitable conventional lost circulation materialsinclude, but are not limited to, asphaltenes, ground coal, cellulosicmaterials, plastic materials, and the like. In certain exemplaryembodiments, the conventional lost circulation materials may be providedin particulate form. One of ordinary skill in the art with the benefitof this disclosure will recognize the appropriate amount of theconventional lost circulation material for a chosen application.

Optionally, additional additives may be added to the cement compositionsof the present invention as deemed appropriate by one skilled in theart, with the benefit of this disclosure. Examples of such additivesinclude, inter alia, fly ash, silica, fluid loss control additives,surfactants, dispersants, accelerators, retarders, salts, mica, fibers,formation-conditioning agents, bentonite, expanding additives,microspheres, weighting materials, defoamers, and the like. For example,the cement compositions of the present invention may be foamed cementcompositions comprising one or more foaming surfactants that maygenerate foam when contacted with a gas, e.g., nitrogen. An example of asuitable fly ash is an ASTM class F fly ash that is commerciallyavailable from Halliburton Energy Services of Dallas, Tex. under thetrade designation “POZMIX® A.” An example of a suitable expandingadditive comprises deadburned magnesium oxide and is commerciallyavailable under the trade name “MICROBOND HT” from Halliburton EnergyServices, Inc., at various locations.

An example of a composition of the present invention comprises a cementcomposition comprising a hydraulic cement, an inelastic lost circulationmaterial, and water.

Another example of a composition of the present invention is a lostcirculation material comprising inelastic polyethylene, polystyrene,and/or polypropylene particles.

To facilitate a better understanding of the present invention, thefollowing examples of exemplary embodiments are given. In no way shouldthe following examples be read to limit, or to define, the scope of theinvention.

EXAMPLE 1

Sample cement compositions were prepared by mixing a base cement slurrywith a variety of lost circulation materials. After sample preparation,the samples were allowed to cure over a 7-day period, during which timecompressive strength tests were performed at selected time intervals at60° F. in accordance with API Specification 10, RP 8.3, RecommendedPractices for Testing Well Cements.

Sample Composition No. 1 comprised 94 pounds of TXI Class C cement, 4%calcium chloride bwoc, 3% liquid sodium silicate bwoc, and 14.51 gallonsof water.

Sample Composition No. 2 comprised 94 pounds of TXI Class C cement, 4%calcium chloride bwoc, 3% liquid sodium silicate bwoc, 5 pounds of a50/50 mixture of ground waste FORMICA® material, and 14.51 gallons ofwater.

Sample Composition No. 3, a cement composition of the present invention,comprised 94 pounds of TXI Class C cement, 4% calcium chloride bwoc, 3%liquid sodium silicate bwoc, 5 pounds of a 50/50 mixture of fine-sizedand medium-sized waste polyethylene particles, and 14.51 gallons ofwater.

The results of the testing are set forth in the table below.

TABLE 1 Compressive Strength (psi) at 60° F. Material 24 Hours 48 Hours72 Hours 7 Days Sample Composition No. 1 155 303 353 543 SampleComposition No. 2 192 287 358 491 Sample Composition No. 3 149 329 390574

The above example demonstrates, inter alia, that the cement compositionsof the present invention comprising inelastic lost circulation materialsmay be suitable for use in cementing operations in subterraneanformations.

EXAMPLE 2

Sample Composition No. 4, a cement composition of the present invention,comprised 600 grams of Class H cement and 31.91 grams of a 50/50 mixtureof medium and fine inelastic polyethylene particles. Sample CompositionNo. 4 was passed through a series of ASTM mesh sieves ranging from 4mesh to 325 mesh arranged in progression. At each stage of theprogression, the amount of the sample composition retained in theindividual sieves was determined. The results of this testing are setforth in the table below.

TABLE 2 Dry Blend Weight of Sieve Sieve Size Empty Weight Sieve WeightBlend on Sieve Number (inches) (grams) (grams) (grams) 4 0.05 529.4529.3 −0.1 18 0.0394 398.3 431 32.7 35 0.0197 316.8 321.5 4.7 50 0.0117291.3 476.4 185.1 325 0.0017 352.1 756.3 404.2

The above example demonstrates, inter alia, that the cement compositionsof the present invention comprising improved lost circulation particlesmay be useful in preventing fluid loss through various voids and vugs ina subterranean formation.

EXAMPLE 3

Sample cement compositions were prepared by mixing a base cement slurrywith a lost circulation material in accordance with the followingprocedure. The base cement slurry comprised a cement that comprised55.9% Class H cement by weight, and 44.1% POZMIX® A by weight. Additivesto this cement included 5% bentonite bwoc, 0.1% HR®-5 bwoc, and 0.75%HALAD®-344 bwoc, and sufficient water to provide a slurry having adensity of 13.24 pounds per gallon. HALAD®-344 is a fluid loss controladditive, and HR®-5 is a set retarder, both commercially available fromHalliburton Energy Services, Inc., at various locations. Testing wasperformed in accordance with API Recommended Practice 10 B, effectivedate Oct. 1, 2002.

Sample Composition No. 5 consisted of the base cement slurry describedabove with no lost circulation material included.

Sample Composition No. 6, a composition of the present invention, wasprepared by mixing the base cement slurry with 5.3% inelasticpolyethylene particles bwoc.

The results of the testing are set forth in the table below.

TABLE 3 Composition Thickening Time (hr:min) Sample Composition No. 55:15 Sample Composition No. 6 4:50

The above example demonstrates, inter alia, that the cement compositionsof the present invention comprising inelastic polyethylene particles maydemonstrate thickening times that are suitable for use in subterraneanoperations.

Therefore, the present invention is well adapted to carry out theobjects and attain the ends and advantages mentioned as well as thosethat are inherent therein. While the invention has been depicted anddescribed by reference to exemplary embodiments of the invention, such areference does not imply a limitation on the invention, and no suchlimitation is to be inferred. The invention is capable of considerablemodification, alternation, and equivalents in form and function, as willoccur to those ordinarily skilled in the pertinent arts and having thebenefit of this disclosure. The depicted and described embodiments ofthe invention are exemplary only, and are not exhaustive of the scope ofthe invention. Consequently, the invention is intended to be limitedonly by the spirit and scope of the appended claims, giving fullcognizance to equivalents in all respects.

1. A well cement composition, comprising: a hydraulic cement; aplurality of inelastic lost circulation material particles comprising agranulated waste material, wherein the granulated waste materialcomprises polyethylene and wherein the plurality of inelastic lostcirculation material particles comprise a mixture of coarse-sizedparticles having an average size greater than about 1,100 microns andparticles selected from the group consisting of fine-sized particleshaving an average size of less than about 150 microns, medium-sizedparticles having an average size in the range of from about 250 micronsto about 850 microns, and combinations thereof; and water in an amountsufficient to form a pumpable slurry.
 2. The well cement composition ofclaim 1 wherein the water is present in the cement composition in anamount in the range of from about 40% to about 50% by weight of thecement.
 3. The well cement composition of claim 1 wherein the water ispresent in the cement composition in an amount in the range of fromabout 30% to about 180% by weight of the cement.
 4. The well cementcomposition of claim 1 wherein the hydraulic cement comprises at leastone material selected from the group consisting of a Portland cement, apozzolanic cement, a gypsum cement, a calcium phosphate cement, a highalumina content cement, a silica cement, and a high alkalinity cement.5. The well cement composition of claim 1 wherein at least one of theinelastic lost circulation material particles comprises a wastepolyethylene particle.
 6. The well cement composition of claim 1 whereinthe plurality of inelastic lost circulation material particles has aparticle size distribution in the range of from about 100 microns toabout 5,000 microns.
 7. The well cement composition of claim 1 whereinthe inelastic lost circulation material particles are present in thecement composition in an amount in the range of from about 4 pounds toabout 6 pounds per sack of the cement.
 8. The well cement composition ofclaim 1 wherein the inelastic lost circulation material particlescomprise about 45% to about 55% of the fine-sized particles by weight ofthe inelastic lost circulation material particles.
 9. The well cementcomposition of claim 1 wherein the inelastic lost circulation materialparticles comprise about 45% to about 55% of the medium-sized particlesby weight of the inelastic lost circulation material particles.
 10. Thewell cement composition of claim 1 wherein the inelastic lostcirculation material particles comprise about 45% to about 55% of thecoarse-sized particles by weight of the inelastic lost circulationmaterial particles.
 11. The well cement composition of claim 1 whereinthe water is present in the cement composition in an amount in the rangeof from about 40% to about 50% by weight of the cement; wherein theinelastic lost circulation material particles are present in the cementcomposition in an amount in the range of from about 4 pounds to about 6pounds per sack of the cement wherein the inelastic lost circulationmaterial particles have a particle size distribution in the range offrom about 100 microns to about 5,000 microns; and wherein the cementcomposition has a density in a range of from about 4 pounds per gallonto about 20 pounds per gallon.
 12. A well cement composition,comprising: a hydraulic cement; a plurality of inelastic lostcirculation material particles comprising granulated waste polyethylene,wherein the plurality of inelastic lost circulation material particlescomprise coarse-sized particles having an average particle size ofgreater than about 1,100 microns; a fluid loss control additive; andwater in an amount sufficient to form a pumpable slurry.
 13. The wellcement composition of claim 12 wherein the water is present in thecement composition in an amount in the range of from about 30% to about180% by weight of the cement.
 14. The well cement composition of claim12 wherein at least one of the inelastic lost circulation materialparticles comprises a waste polyethylene particle.
 15. The well cementcomposition of claim 12 wherein the plurality of inelastic lostcirculation material particles has a particle size distribution in therange of from about 100 microns to about 5,000 microns.
 16. The wellcement composition of claim 12 wherein the inelastic lost circulationmaterial particles are present in the cement composition in an amount inthe range of from about 4 pounds to about 6 pounds per sack of thecement.
 17. The well cement composition of claim 12 wherein theinelastic lost circulation material particles comprise about 45% toabout 55% fine-sized particles by weight of the inelastic lostcirculation material particles, the fine-size particles having anaverage size in the range of less than about 150 microns.
 18. The wellcement composition of claim 1 wherein the inelastic lost circulationmaterial particles comprise about 45% to about 55% medium-sizedparticles by weight of the inelastic lost circulation materialparticles, the medium-sized particles having an average size in therange of from about 250 microns to about 850 microns.
 19. The wellcement composition of claim 1 wherein the inelastic lost circulationmaterial particles comprise about 45% to about 55% of the coarse-sizedparticles by weight of the inelastic lost circulation materialparticles.
 20. The well cement composition of claim 12 wherein theinelastic lost circulation material particles comprise fine-sizedparticles having an average size in the range of less than about 150microns.
 21. The well cement composition of claim 12 wherein theinelastic lost circulation material particles comprise medium-sizedparticles having an average size in the range of from about 250 micronsto about 850 microns.
 22. The well cement composition of claim 1 whereinthe inelastic lost circulation material particles comprise thefine-sized particles.
 23. The well cement composition of claim 1 whereinthe inelastic lost circulation material particles comprise themedium-sized particles.
 24. A well cement composition, comprising: acement, inelastic lost circulation particles comprising a mixture ofcoarse-sized particles having an average size greater than about 1,100microns and particles selected from the group consisting of fine-sizedparticles having an average size of less than about 150 microns,medium-sized particles having an average size in the range of from about250 microns and 850 microns, and combinations thereof and water.
 25. Thewell cement composition of claim 24 wherein the cement comprises ahydraulic cement.
 26. The well cement composition of claim 24 whereinthe inelastic lost circulation particles comprise at least one materialselected from the group consisting of polyethylene, polypropylene, andpolystyrene.
 27. The well cement composition of claim 24 wherein atleast one of the inelastic lost circulation particles comprises a wasteparticle.
 28. The well cement composition of claim 27 wherein the wasteparticle comprises polyethylene.
 29. The well cement composition ofclaim 24 wherein the inelastic lost circulation particles comprise about45% to about 55% of the fine-sized particles by weight of the inelasticlost circulation material particles.
 30. The well cement composition ofclaim 24 wherein the inelastic lost circulation material particlescomprise about 45% to about 55% of the medium-sized particles by weightof the inelastic lost circulation material particles.
 31. The wellcement composition of claim 24 wherein the inelastic lost circulationparticles comprise about 45% to about 55% of the coarse-sized particlesby weight of the inelastic lost circulation particles.
 32. A well cementcomposition, comprising: a cement; inelastic lost circulation particlescomprising coarse-sized particles having an average size greater thanabout 1,100 microns; a fluid loss control additive; and water.
 33. Thewell cement composition of claim 32 wherein the cement comprises ahydraulic cement.
 34. The well cement composition of claim 32 whereinthe inelastic lost circulation particles comprise at least one materialselected from the group consisting of polyethylene, polypropylene, andpolystyrene.
 35. The well cement composition of claim 32 wherein atleast one of the inelastic lost circulation particles comprises a wasteparticle.
 36. The well cement composition of claim 35 wherein the wasteparticle comprises polyethylene.
 37. The well cement composition ofclaim 32 wherein the inelastic lost circulation particles comprisefine-sized particles having an average size in the range of less thanabout 150 microns.
 38. The well cement composition of claim 32 whereinthe inelastic lost circulation particles comprise medium-sized particleshaving an average size in the range of from about 250 microns to about850 microns.
 39. The well cement composition of claim 32 wherein theinelastic lost circulation particles comprise about 45% to about 55%fine-sized particles by weight of the inelastic lost circulationparticles.
 40. The well cement composition of claim 32 wherein theinelastic lost circulation particles comprise about 45% to about 55%medium-sized particles by weight of the inelastic lost circulationparticles.
 41. The well cement composition of claim 32 wherein theinelastic lost circulation particles comprise about 45% to about 55% ofthe coarse-sized particles by weight of the inelastic lost circulationparticles.